


Study You

by LittleQuail



Category: Undertale (Video Game)
Genre: Cunnilingus, Multiple Orgasms, Other, POV Second Person, Porn With Plot, Tentacles, first chapter is just setting stuff up, reader has a vagina and boobs, second chapter is where the fun begins
Language: English
Status: Completed
Published: 2015-11-18
Updated: 2015-11-19
Packaged: 2018-05-02 07:02:34
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,072
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5238908
Author URL: https://archiveofourown.org/users/LittleQuail/pseuds/LittleQuail
Summary: <blockquote class="userstuff">
              <p>The good doctor notices that you've been reading a lot about him..</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> This is kind of just something that I wanted and didn't see enough of? I just know that I am stupidly in love with this void man and just want more. Thank you for reading!

It’s been about a month since you had fallen in love with a new video game called Undertale. You didn’t think much of it when you first saw it, just that it was a silly rpg that was pretty cheap and everyone and their dog seemed to be playing it. You bought it and went through your first run - a neutral run on accident. Then, a pacifist run, where you fell in love with all the characters and their dialog, getting every piece of it you could. You didn’t dare do a no mercy run, you simply wanted to let everyone stay happy. You had heard of how the game would remember if you killed everyone throughout other playthroughs, which scared you to say the least. 

Across this obsession of yours, you had run into a character that could only be found by changing some of the code in the game. A secret gray room between hallways in Waterfall would be opened and a sprite you had never seen before would be in it. W. D. Gaster. He had intrigued you ever since you had heard the name and you had become enamored with him immediately. 

After a long day of class, you were happy to be back in your room, and you flopped on your bed, kicking off your shoes and relaxing. Stretching your arms behind your back and closing your eyes, you stretched the rest of your body and heard some satisfying pops from your hips and back. Something in the other corner of your room made a noise between a grunt and a moan, and your eyes popped open in panic. You sat up quickly, making your head spin a little, and searched for the source of the sound. Finding nothing, your heart began to slow and you started to lay back down. 

Something was behind you. 

You felt it before you saw it. A large figure had somehow gotten behind you on your bed and now you could feel hands on your shoulders. You tensed up, turning your head slowly to see the hands had holes in the palms, your own getting sweaty with fear. You kept twisting, having to tilt your head up to see the head of the person(?) behind you. With cracks in his skull and no pupils, your mind started to scream at you to run, but something in you knew him very well.

You cracked a small smile, though your eyes were filled with fear, and pushed out a “G-Gaster?” His own mouth grew into a grin and his grip on your shoulders tightened.

[DON’T BE AFRAID. I HAVE BEEN WATCHING YOU FOR QUITE SOME TIME NOW. IT IS NO SURPRISE YOU KNOW WHO I AM.] His voice was more electronic than you expected, filled with static. [IT SEEMS LIKE YOU HAVE BEEN.. STUDYING ME.]

You pressed your lips together and considered it. “Kind of? I-I mean, you’re very interesting, it’s hard not to get intrigued, I guess.” You thought back to all the fanart and theories you had seen and read and realized some of them had been less than family friendly. Your cheeks began to show red, your ears following suit. Gaster noticed and his smile turned into a smirk.

[YES, I KNOW ABOUT THOSE AS WELL. HUMANS ARE VERY.. FASCINATING WHEN IT COMES TO WHAT THEY’RE ATTRACTED TO. WHO WOULD HAVE THOUGHT A SAD SCIENTIST FROM THE VOID WOULD GET SO MUCH ATTENTION.] His hand slid down your arm and ended at your wrist, bringing your palm up to his mouth and nuzzling it against his teeth, trying to give it a kiss. [IT SEEMS LIKE YOU HAVE TAKEN A LIKING TO ME.] 

You nodded hesitantly, looking away in shame. Being caught made you feel like a little school girl talking to her crush and you couldn’t believe yourself. To be honest, you couldn’t believe that any of this was happening at all. But you were instantly brought back from your thoughts when two bony fingers reached under your chin and brought your face back to his. He was much closer to you now, nearly inches away. Without thinking, you leaned in quick and gave him a smooch on his mouth, pulling back as your blush threatened to take over your entire face. The rest of his hand grabbed your chin and tugged you back to him, pressing his skull to your lips. He was trying his hardest to kiss you, so you gave it your all as well. It was only when something wet touched your lips that you pulled back in surprise, seeing an odd, glowing green tongue wiggling out between his teeth. Oh god, what you wanted that tongue to do. Right now, it seemed obvious what Gaster wanted to do with it though, as he attacked your mouth with it, wanting to taste every corner of your mouth, making you moan in the back of your throat. He wrenched himself away from you and gave you a smirk. 

[I LIKE WHAT I HEAR.. I WANT TO HEAR MORE.] He turned you around, you silently thanking him as your twisting back was starting to hurt. He pushed you down onto your bed, his large and dark frame towering over yours. 

[YOU’VE BEEN STUDYING ME. NOW I WANT TO STUDY YOU.]


	2. Chapter 2

**Summary for the Chapter:**

> Gaster feels like he should be taking notes.

**Notes for the Chapter:**

> Hi I've never written porn before but I've read more than my fair share. Hope you like it ;o; Thank you for reading!

He began by running his hands down your arms, feeling your muscles and bones underneath them. His mouth was on yours to preoccupy you, tongue swirling around with yours, his saliva tasting like a sweet black licorice. Usually that was pretty gross to you, but you were so enraptured by him that he could taste like anything and you’d be turned on. One of his hands ran back up to your shoulder, his fingers grazing your neck, then to your ear, and finally tangling them in your hair. His other hand found its way to your chest, feeling your breast through your shirt. Your back arched up to make him press harder on them, and you could feel him smile through the kiss. 

He reached down to the hem of your shirt, fiddling it before slipping it up and, breaking the kiss, he brought it over your head, tossing it to the side. His eyes traveled from your neck, to your breasts, his hand following his gazes. In a scientific curiosity, he pressed along your muscles, noting your reactions. When he got to your sides, he gave them a little squeeze and you tried to stifle a laugh as it tickled. He noticed your small noises and gave a warm smile, pinching your little love handles more and you couldn’t take it. You burst out in giggles and squirmed in his grasp. He continued for a few moments until he was satisfied and he bent down to give you a quick kiss as a consolation. 

He reached a hand behind you and lifted you up just enough for him to unclasp your bra. He let you down gently and slipped off the undergarment. His hands went straight to your breasts, massaging one while the other’s nipple got the same treatment. You let out a quiet moan, hands flying up to your mouth to cover such a lewd sound. He let go of your mounds and pulled your hands away.

[DON’T BE QUIET FOR ME, I WANT TO HEAR ALL YOUR SOUNDS], he demanded, you giving him a small nod before he continued with his work. He bent his head down to give small licks to one of your buds, making you let out a small gasp of pleasure. He gave one attention and massaged the other one for a few seconds before switching, making shivers run down your back. One of his hands slid down your side, resting at your hip. He gave your chest a well needed break and brought his face back up to yours. 

[I WANT TO EXPLORE ALL OF YOU, BUT ONLY IF IT’S OKAY WITH YOU.] His voice was getting rougher as the two of you grew hotter with lust. He toyed with the waist of your pants, gliding his hand around your thigh and finally pressing against your warmth. 

You groaned out, “Yes, of course, please Gaster, please touch me!” As a sign of his understanding, he hooked his thumbs into your pants and tugged them down, throwing them to the side as well. Goosebumps rose on your legs as cold air hit them, sending another shiver through you. He explored your thighs, knees, rubbing little circles on your ankles, before heading back up to the goal. 

He kept his good eye on you as he lowered himself down between your legs, watching your face flush with anticipation. He turned his attention back to your underwear, giving a lick from bottom to top. You gasped and wiggled your hips to get him to continue. Instead, he pulled down your panties and came face to face with what he wanted. He brought a bony finger to your folds and pressed against your clit, giving a grin as you moaned out and squirmed around. He rolled it around in his fingers, his tongue making quick work of your heat. You could feel yourself getting wetter as warmth pooled in your stomach and your climax threatened to overtake you. He could sense you were close, and pushed two fingers into you, pushing you over and making you arch your back. You moaned out Gaster’s name and clenched around him, your thighs squeezing his head as you rode out your orgasm. Once it was finished, you let him go, trying to catch your breath. He brought his fingers out of you and kissed you deep, making you taste yourself on his tongue. 

[THERE ARE MANY WAYS TO MAKE YOU COME, AREN’T THERE, HUMAN? LET’S FIND THE OTHER ONES.] Before giving you a chance to rest, you felt something against your sensitive entrance. You glanced down between your legs and saw a slick, black tentacle coming out from the doctor. [I AM NOT LIKE HUMAN MALES, BUT I HOPE THIS WILL BE SATISFACTORY.] With that, he started to push into you. 

“C-couldn’t you, aah, give me a, a little time to recov-aAH” He thrusted all the way inside of you and the feeling of his erection was incredible. It was different than any other toy you had ever used, this was more slimy and wiggled around inside. It pressed against the spot inside of you that you had never been able to reach, and you let out a quick scream, your back arching off the bed by a good few inches. You felt the endorphins rush through you as he pulled out and back in, hitting the spot with each lunge. 

“G-Gaster!” you yelled out his name, and something in his eyes shined. 

[SAY IT AGAIN] he demanded, slowing his thrusts. 

“Gaster! O-oh, Gaster please, keep going!” He did as you asked, slamming back into you and making you groan. A hand floated down to your nub, rubbing it between his fingers and he kept hitting your gspot over and over again. It wasn’t long before you could start seeing stars behind your eyes.

“G-Gaster I can’t- I’m gonna c-co-come!” With that, something inside you snapped and your vision flashed white, your walls clenching against the tentacle. It took Gaster a couple more thrusts before he came as well, something cold and sticky coating your insides. He stayed inside of you while you rode out the waves of your orgasm. You gave a sigh as you could feel it subsiding, and he pulled out, bringing some of the back goop with him. A snap of his fingers and both the tentacle and the substance coming out of it disappeared, leaving you with a residual cold temperature in you. 

He leant down and gave you one last kiss before cupping your cheek and whispering in your ear. [THANK YOU FOR LETTING ME STUDY YOU. I HOPE I CAN DO IT AGAIN SOMETIME.] You gave a weak nod, your mind still foggy and tired. He pulled the blanket up over you in your bed and you fell asleep, absolutely tuckered out.

In the morning when you woke up, you noticed that your clothes from the night before had been folded and put by your laundry basket. New clothes had been laid by your bed. You gave a wistful sigh and smiled, hoping to never forget that incredible experience.


End file.
